Power Systems T...

In the overhead line insulator string, for improving string efficiency

1. Long cross arms are used

2. In the capacitance grading method, to improve the string efficiency, unit near the cross arm should have maximum capacitance and the unit near the conductor should have minimum capacitance

3. Guard ring is used

Which of the above is/are correct?

Determine the economic overall diameters (in cm) of a 1-core cable metal sheathed for a working voltage of 100 kV if the dielectric strength of the insulating material is 80 kV/cm.

In a three core cable, the capacitance between two conductors (with sheath earthed) is 1 μF. The capacitance per phase (in μF) will be

The capacitance per kilometre of a three-phase belted cable is 0.18 μF between two cores with the third core connected to sheath. The kVA taken by 20 km long cable when connected to three-phase, 50 Hz, 3300 V supply is ________ (in kVA)

The insulation resistance of a single-core cable is 495 MΩ per km. If the core diameter is 2.5 cm and resistivity of insulation is 4.5 × 10¹⁴ Ω-cm. The thickness of insulation in cm, is ________ (up to two decimal places)

Calculate the charging current (in A) of a single core cable used on a 3-phaes 66 kV system. The cable is 2 km long having a core diameter of 14 cm and an impregnated paper insulation of thickness 10 cm. The relative permittivity of the insulation may be taken as 4 and the supply at 50 Hz.

A 33 kV, 50 Hz, three-phase underground cable, 4 km long, uses three single core cables. Each of the conductors has a diameter of 2.5 cm and the radial thickness of insulation is 0.5 cm. The relative permittivity of the dielectric is 3.0. If the power factor of the unloaded cable is 0.02, the dielectric loss per phase in kW is _______